Christopher Green, an observer of North Korea, was quoted in the Washington Post speculating that "the piece, which was likely made by South Korean sympathizers in conjunction with their Northern pals, is designed to encourage pro-North groups in the South and stoke the flames of anti-U.S. sentiment in broader South Korean society."
Here’s the text from the video, translated into English by NKNews:
North Korea has succeeded in proceeding with this nuclear test despite the United States’ increasingly unfair bully activities against North Korea. That United States that has no respect to others nor appreciation to equality…
It is not incorrect to state that the United States strong hostility policy and endless violence toward North Korea in the past 70 years has helped North Korea become one of the world’s strongest military power states.
Words spoken by the United States, a country that uses the law of jungle as the law of survival for fitness, is meaningless. As a result, North Korea’s high level nuclear test conducted against American imperialist invaders is a nuclear deterrent that protects our sovereignty.
Thus, the United States has practically guided North Korea towards nuclear testing and therefore needs to be considered as an American virtue.
North Korea’s third underground nuclear test! Let it be known once more that this is strictly our practical counter-measure for North’s safety and to protect its sovereignty from the aggressors. It is also a solemn warning that time is no longer on the side of the United States.
The people are watching. America should answer.